Hob grinding machine



J. EDGAR HOB GRINDING MACHINE 5 Sheets-Sheet 1 Original Filed June 28,1916 J. EDGAR HOB GRINDING MACHINE 5 Sheets-Sheet 2 Original Fild Jun e28, 1916 Nov. 10, 1931.-

J. EDGAR HOB GRINDING MACHINE ,5 Sheets-Sheet 3 Nov. 10, 1931.

Original Filed June 28, 1916 ewr':

' J. EDGAR HOB GRINDING MACHINE 5 Sheets-Sheet 4 Nov. '10, 1931.

Original Filed June 28, 191

J. EDGAR HOB GRINDING MACHINE I 5 Sheets-Sheet 5 Nov. 1-0, 1931.

Original Filed June 28, 1916 Reissued Nov. 10, 1931 UNITED. STATESPATENT OFFICE JOHN EDGAR, or. RocKroRn; I'LLINQIs; v ASSIGNOR, BY MESNEAssIGNMEN'rs, mo BARBER-COLMAN COMPANY, OF ROCKFORD, ILLINo s, aCORPORATION or ILLINoIs HOB GRINDING MACHINE Original No. 1,561,064,dated November 10, 1925, Serial No. 106,339, filed June 28, 1916.Application for reissue filed April 20', 1931. Serial No. 531,653.

This invention relates to the manufacture of hobs used in generatingspur and spiral gear wheels. After thepartially-completed hobs have beenhardened, it is necessary to grind the teeth of the hobs to give themcorrect form and dimensions.

The objectof this invention is to produce a machine by means of whichthe teeth of a hob may be quickly and accurately ground to orm and size.

, lieved cutting teeth, the cutting faces of the teeth being defined bygashes which ma-y be "either straight (i. e. parallel with the axis ofthe hob) or spiral. In order that the hob shall have relatively longlife, a'circumferenthe narrowness of the gashes it is impracticatiallength of the teeth is made as great'as possible, which means that thegashes are relatively narrow-much narrower, proportionately, than in thecase of a tap, for instance. Because of the length of the teeth, thereis considerable difference between the height of a tooth at its frontend and its height at its rear end, which fact necessitatesa relativelylong relieving stroke and an' abrupt return stroke. Moreover, because ofwheel so that its periphery may be employed in grinding.

The machine herein disclosed is speciallyadapted to fulfill therequirements peculiar to the grinding of hobs, straight-gashed as wellas spiral-gashed, and to produce accurate work at a relatively fast rateand with a minimum of interruption for .dressing the grinding element.-

In the accompanying drawings, Figure 1 is a top plan view of ahob-grinding machine embodymg the features of my inventlon.

A hob has one or more spiral series of re,

Fig. 1 is a fragmental sectional view of the tail stock of the machine.

Fig. 1 illustrates the position of the grinding wheel with relation tothe hob.

Fig. 2 is a sectional view of the connection between the hob slide andthe feed-screw for moving said slide,

the view being taken in the plane of dotted line 2-2 of Fig. 5.

Fig. 3 is a fragmental side elevation of the machine.

Fig. 1. is a section taken in the plane ofdotted line 4 of Fig. 1.

Fig. 5 is a section taken in the plane of dot tedline 5 of Fig. l. p

Fig. 5 is a View of a clamp for the wheelcarrying head.

Fig. 6 is a section on dotted line 6 of Fig. 1.

Fig. 7 is a horizontal central sectional view of the hobsupportingmeans.

Fig. 8 is a view looking from the left-hand end of Fig. 3.

Fig. 9 is a sectional view of the means for rotating the hob.

Fig. 10 is a view of the means for indexing a plural-thread hob.

Fig. 1-1 is a section on Fig. 4. I a

Fig. 12 is a section Fig. 4.

Fig. 13 is a section Fig. 14..

Fig. 14 is a section dotted line ii of on dotted line 12 of on dottedline 13'of on dotted line 14 of Fig.1.

Fig. 15 is a section Fig. 5.

Figs. 16 and 17 are views of an attachment for dressing the grindingwheel.-

Fig. 18 is atop plan view of the dressing attachment.

Fig. 19 is a view showing the dressing tool in operative relation to thegrinding-wheel.

Fig. 20 is a fragmental view looking from the right-hand side of Fig.17.

Fig. 21 is a section on dotted line 21 of Fig. 16. i

Referring to the top plan view entitled Fig. 1 LAlIldlCEltGS a hob and agrinding wheel. In operation, the grinding at high speed. The hob A isslowly rotated in the opposite direction and is also given a on dottedline 15 of wheel B is rotated said bolt lying within a supported acorrespondingly tapered past the grinding wheel, the hob is returned toinitial position and adjusted with relation to the grinding wheel sothat the latter shall be able to remove more material. The hob isthenrotated and fed past the grinding wheel asbefore. I These operations arerepeated until one side of the thread of the hob has been completelyground. The head that carries the grinding wheel is then reversed so asto place the grinding wheel in position to grind the other side ofthethread of the hob. The hob is then fed past the grindingwheel thedesired number of times until the last mentioned side of the thread hasbeen properly ground. f

A slide 1,.upon which the hob is supported, is mounted upon'two guides 2and 3 (F1 5) formed upon the bedof the mach ne. pon the slide 1 is aheadstock 4 and a tailstock 5, the latter bein adjustable toward andaway from the hea stock upon a guide 6. The

tailstock is secured to the slide 1 in adjusted position by means of abolt 7 (Fig. 1) extending through the tailstock, the head of T-slot 8 inthe slide. A spindle 9 (Figs. 1, 3 and 7) is rotatably in the headstock4 and is held against longitudinal movement in said headstock by meansof a flange 10 and a collar 11. The spindle 9 is made tubular to permitof inserting and removing the support or arbor 12 that carries the hob.The arbor 12 has a tapered portion adapted to be driven into socket inthe end of the spindle 9. The. spindle 'being tubular, as shown in Figs.7 and 9, a rod may be 1nserted into the other end of the spindle for thepurpose of driving out the arbor 12 when necessary. The hob is securedupon the arbor between an annular shoulder 13 and a I nut 14, and isfurther held against rotation with relation to the arbor by means of akey 15. The end of the arbor opposite to the tapered end is providedwith a center 16 arranged to be rotatably supported by a sleeve 17carried by the tailstock 5. Said sleeve is held against rotation bymeans of a key 18 and is arranged to be moved into and out of o rativerelation to the center 16 by means 0 a screw 19 having an operating handwheel 20. Clamp members 17 (Fig. 1) and a screw 17 provide means forsecurely locking the sleeve 17 against movement.

The means for rotating the spindle 9 comrises a sleeve 21 (Fig. 9)rotatably mounted in bearings 22 and 23 in the supporting framework ofthe machine. The spindle 9 is slidable longitudinally of the sleeve 21,

the spindle. By means to be later described,

the sleeve 21; is adjustably connected (to a gear Wheel 26 that mesheswith a pinion 27 (F ig, 1) fixed on the drive shaft 28. On.

said shaft is secured a stepped pulley 29. Said pulley is driven from areversible countershaft (not shown) or. other suitable source of power.

The means for feeding the slide 1 coinprises a feed screw 30 (Figs. 4and 5) supported in a bearing 31 in the machine frame. Rigid with theslide 1 are two downwardly extending lugs 32 (Figs. 2 and 5). A bearing33 lies between these lugs. and has flanges 34 to cause the lugs andbearing to travel together. Rotatably mounted in the bearing 33 is a nut35, said nut being held against endwise movement with relation to thebearing 33 by means of a shoulder=36 and a nut 37 The nut 35 is threadedupon a-nut 38 on the feed screw 30. The nut 38 is prevented fromrotating with relation to the bearing 33 by means of an arm 39 which isrigid with said nut, said arm having an opening through which a pin 40is slidable (see Fig. -4),'sa1d pin being fixed in the bearing 33 andextending longitudinally of the feed screw 30. When the feed screw 30 isrotated, the nut 38 will becaused to move longitudinally of said feedscrew, the nut 38 carrying with it the nut 35, the bearing 33 andthelugs 32, and thus imparting movement to the slide 1. I

- In order that the slide 1 shall be adjustable with relation to the nut38 I provide a shaft 41 rotatably supported in the slide 1 and having 11on its lower. end spiral gear teeth 42 meshing with similar teeth 43formed upon the nut 35. The upper end of the shaft 41 1s squared toreceive a crank. Fixed to the shaft 41 is a micrometer dial 44 arrangedto coact with a zero mark on the adjacent. portion of the slide. Afterthe "wheel B has made a cut and the slide 1 has been returned,

the slide may be adjusted by means of the shaft 41 to permit thegrinding wheel B to make'another cut on the same side of the thread ofthe' hob. 1

The feed screw 30 is arranged to be rotated by power means for advancingthe hob with relation to the grinding wheel and is also arranged to berotated by manually acios tuated means for the purpose of returning theslide l to initial position; said manually actuated means comprises a'shaft 45 (Figsi 1, 3 and 4), said shaft being connected to the feedscrew 30 by meansof spiral gears 46 and the outer end of said shaftbeing squared to receive a crank.

The power means for rotating the feed screw 30 comprises a clutch shaft47 (Fig. 4)

I alined with and supporting one end of the .fecd screw 30 and having aclutch face 48 ar nally of the feed screw 30 by means of a fork 51engaging said clutch member and fixed upon a rock shaft 52. Upon theouter end of the rock shaft 52 is fixed a hand crank 53 (Fig. 3). Afterthe clutch member 49 has been disengaged from the clutch shaft 47, theshaft may be rotated to adjust the slide 1 to place the hob inapproximately operative relation to the grinding wheel. Fixed to theclutch shaft 4-7 is a change-gear 54 (Figs. 1 and 8) meshing with achange-gear 55; the latter gear is rigid with a change-gear that mesheswith a change-gear56; the changegear 56 is rigid with a gear 57 thatmeshes with a gear 58 which is rigid with the gear 2-6; the latter, itwill be remembered, meshes with a pinion 27 on the drive shaft 28.

A hob may have one or a plurality of threads. After one thread of amultiple thread hob has been ground, it- IS necessary toturn the hob tobring another thread into position to be ground. For this purpose thespindle 9 is adjustably connected to the gear wheel 26. Rigid with thesleeve 21 in a flange or disk 59. A ring 60 is adjustably secured to thedisk 59 by means of bolts 61 extending through the disk 59 and havingheads that lie within circular under-cut slots 62 in the ring60. Thering 60 is adj ustably secured to the gear wheel 26 by similar clampbolts 63.

gear wheel 26 there is provided a springpressed index pin 64 carried bythe gear wheel 26 and arranged to enter any one of a number of openings65 in the ring 60. When one thread of a double-thread hob has beenground, the clamp bolts 63 are loosened, the

index pin Oddrawn back and the ring 60 turned through one-half of arevolution, thus bringing an opening 65 into register with the index pin6%, which latter is then permitted to spring into said opening. In thecase of a triple thread hob the operator would turn the ring 60 withrelation to the gear wheel 26 through one-third of a revolution, thusbringing an opening 65 into register with the index pin 64. For thusturning the ring 60, a bar (not shown) would be inserted in openings 21(Fig. 9) in a collar on the sleeve 21. Any desired number or arrangementof openings 65 may be provided to take care of hobs having variousnumbers of threads.

In order that the spindle 9 may be adjusted for hobs having a number ofthreads not provided for by the spacing of the openings 65, the disk 59and the ring60 are adj ustably connected together as hereinbeforestated.

A graduated ring 66 is rotatably mounted upon the periphery of the disk59 and is secured thereto in adjusted position by means of a clamp bolt67. On the ring 60 is a Vernier 68. Normally the zero line on the ring66 is opposite the zero line of the vernier 68. After one thread of ahobhaving such special number of threads has been ground, the hob is turnedto bring the next thread into position to be acted upon by the wheel Bby loosening the clamp bolt 61 and turning the disk 59 with reference tothe Vernier 68 through an arc of the necessary length. The

clamp bolts 61 are then tightened, the bolt 67 slackened, the ring 66returned to zero position and the bolt 67 again tightened. lVhcn thenext thread is to be ground, the flange 59 is again turned withreference to the vernier 68 through the same angular distance as before.

The adjustable connection between the flange 59 and the ring 60 affordsmeans for conveniently setting the hob with relation to the relievingcam 71 so that as the hob rotates the grinding wheel shall be movedoutwardly in time to begin operation on each succeeding tooth.

The grinding wheel B is carried by a slide 69 (Figs. 1 and 5) which isreciprocable at right angles to the direction of movementof the slide 1.As shown in Fig. 5, the teeth of the hob A are relieved with a uniformclearance. As a tooth revolvespast the wheel B, the slide 69 is movedtoward the slide 1 to maintain the wheel in proper relation to thetooth. As soon as the tooth has passed the wheel the slide 69 is given aquick outward movement to place the wheel B in position to grind thenext succeeding tooth. The means for thus reciprocating the slide 69comprises a shaft 70 (Figs. 1, 3 and 5)- carrying a cam 71 arranged tooperate against a block 72 upon the slide 69. As shown in Fig. 14, theshaft 70 is made in two sections connected by the one-way clutch 7 3shown in Fig. 13, in order that the cam 71 shall not interfere withreverse movement of the rest of the machine when it is desirable to turnthe drive shaft 28 backward in adjusting the relation of the hob to thegrinding wheel. The shaft 7O is driven from the drive shaft 28 throughchange gears 74, 75 and 76 (Fig. 8).

The slide 69 is moved away from the hob by means of a coiled compressionspring 77 movementof the slide 69. When the machine is running the slide82 is stationary with relation to the slide 69, but means is providedwhereby the slide and away from the hob when the machine is beingadjusted. Referring to Fig. 5: A bar 83 is fixed to a lug 84 on theslide 69. On the bar 83 is slidably and rotatably mounted an adjustingscrew 85 having holes 85 to receive an implement for turning the screw.The screw 85 is slidably and .rotatably supported in a guide 86 on theslide 69. A coiled compression spring 87 surrounding the bar 83 bears atone end against the lug 84 and at its other end against a portion of thescrew 85. The spring 87 is restrained-by a hand lever 88 (Fig. 1) whichis pivoted to the outer end of the bar 83, said hand lever having a camportion 89 that bears against a washer which in turn lies in contactwith the screw 85. A detent 88" yieldingly locks the handle 88 againstmovement.

It will be seen that I have provided three mutually independent meansfor producing movement of the slide toward and away from the hob,namely, the cam 71 and the spring 7 7 the screw 85, and the hand lever88 and its connections.

The slide 82 is fixed to the screw 85 by the means shown in Figs. 5 and6. 90'is a nut rigidly secured to the slide 82 and engaging the screw85. In order that the nut 90; may be tightly clamped to the screw 85,said nut is splitat one side (as at 91) and is arranged to be contractedinto clamping engagement with the screw by means of a screw 92.

The grinding-wheel spindle is carried by a frame 93 (1 ig. 15) providedwith trunnions 94 which are mounted for oscillation in a bearing 95'onthe slide 82 and in a bushing '96 carried by a portion 97 of the slide82. It

' will be'observed that the bearing 95 and portion 97 of the slidetogether constitute a tool post in which the tool-carrying frame 93 ispivoted upon an axis (1 (Figs. 1 and 15) intersecting the axis b of thehob at a right angle.

intersection 0 of and the line .ofcontact of the hob and the grindingwheel is in the axis a of the trunnions 94. The frame 93 .is arranged tobe held against swinging movement by means of a screw 98 engagin athreaded opening 99 in said frame and a apted to extend through eitherof two diametrically opposite curved slots100 in the slide portion 97.Vhen dressinga grinding wheel that is to be used in grlnding the teethof a spirallyga-shed hob, the frame 93 should be secured in thehorizontal plane of the spindle 9, and for this purpose 1 provide apositioning pin 101 adapted to be inserted into ei her one of twoopenings 102 provided at diametrically opposite points in the portion 97The pin 101 is adapted to enter a hole 103 in the frame 93. The'pin 82may be moved toward \Vhen grinding the hob the point of" the pitch lineat of the hob' 101 is used only in setting the frame 93 preparatory todressin the grinding wheel, and at other times is withdrawn from theopen in s'102 and 103.

or setting the frame 93 at an angle corresponding to the angle of thethread of the hob, I provide a protractor ring 104 (Figs. 1, 5 and 15)rotatably mounted upon the bushing 96 and arranged to be clamped to theportion 97 by means ofbolts 105 extending through the portion 97 andhaving heads lying in an annular T-slot 106 in the protractor ring. Atdiametrically opposite points on the protractor ring are formed notches107 to receive a spring-pressed detent pin l08 carried by the frame 93.For withdrawing thepin 108 from engagement with a notch 107, there isprovided a pinion 109 arranged to engage rack teeth formed on the pin108. The upper end of the pinion 109 is adapted to be engaged by a key110.

The protractor ring 104: is provided with graduations as shown in Fig.1, and the portion 97 is provided with a cooperating zero mark. j

, The grinding-wheel spindle is carried by a power head 111 which ismounted in a clamp on the frame clamp will be apparent from Fig. 5 Thejaw 112 of the clamp is relatively stationary,

been loosened, the head ,111 may be slid back a and forth with relationto the frame 93 by operating nuts 117 on a screw stud 118 fixed totheframe 93, said nuts lying at opposite sides of a lug 119 on the head111.

The grinding wheel B is removably secured in any usual or suitable wayto a spin dle 120 (Fig. 15), the axis of which intersects the axis ofthe frame 93. Said spindle has a tapered portion which lies within acorrespondingly tapered bushing 121 in, the head 111, the spindle beingurged forward against said bushing by means of a coiled spring 122.Fixed to the spindle 120 is a gear wheel- 123 that meshes with a gearwheel 124 on a shaft 93. The construction of this 125 arranged parallelto the spindle and car ried by the head 111. Rigid with the shaft 125 isa bevel gear wheel 126 that meshes wit-h crown gear teeth formed uponone side of a driving pulley 127, said pulley being rotatably mountedupon a stud 128 fixed to the head 111.

spring 87 (Fig. 5) to move the slide 82 outwardly. The frame 93 isadjusted, with the aid of the protractor ring 104, to the properinclination with reference to the angle of the thread of the hob (seeFig. 3), the frame 93 being secured in adjusted position by means of thescrew 98. The tailstock 5 is slid away from the headstock 4. The arbor12 is inserted into the tapered end of the spindle 9. The hob is placedon said arbor and secured thereto by means of thenut 14. The tailstockis slid up to place the end of the sleeve 17 against the center 16. Thenut on the bolt 7 is tightened up to clamp the tailstock in place. Thehand-knob 20 is turned to press the sleeve 17 against the center 16, andthe sleeve is locked in adjusted position by means of the clamp 17. Theclutch 49 being in the thrown-out position, the shaft 45 is rotatedmanually until the side of the forward end of the thread is near theworking portion of the grinding wheel B, after which the clutch 49 isthrown in. The handle 88 is then turned to advance the wheel B towardthe hob. The flange 59 is then adjusted with relation to the ring 60until the hob is in proper relation to the cam 71. The machine is thenset in operation, whereby the wheel B is rapidly rotated, the slide 1slowly advanced, and the spindle 9 slowly rotated. By means of the shaft41 the operator accelerates the feed movement of the slide 1 until thegrinding wheel is making a proper cut. After the hob has been fed pastthe grinding wheel B, the machine is stopped, said wheel is withdrawn byoperating the handle 88, and

the slide 1 is returned to initial position by reversing the drive forthe pulley 29. After the slide has been returned to initial position,the machine is stopped, the wheel B is returned to working position bymeans of the hand lever 88, and the machine again set in operation tofeed the hob past the grinding Wheel. The operator turns the shaft 41 soas toadvance the slide 1 sufliciently to enable the wheel B to make asecond cut of proper depth.

After one side of the thread has been completely ground, the machine isstopped, the clutch 49 thrown out, the wheel B retracted by means of thelever 88, the slide 1 returned by means of the shaft 45, and the clutch49 thrown in. The screw 98 (Fig. 15) is withdrawn; the detent pin 108 isremoved from the notch 107 with which it is in engagement; the frame 93is swung through an arc of 180 degrees until the detent pin 108 springsinto the other notch 107; the screw 98 is inserted into the other slot100 and into the'hole 99 and tightened to secure the frame 93 rigidly inplace. The belt. 129 is then removed from the pulley 127 and twistedand'replaced. The wheel B is then moved forward into grinding position.The slide 1 is then adjustcd to move the hob longitudinally, a distanceapproximately one-half the circular pitch of the hob so as to bring theunground side'of the thread into approximate position to be ground. Themachine is started up and the shaft 41 is turned until the wheel ismaking a proper out. After the second side of the thread has beenmade-smooth, the operator employs at intervals asuitable gauge in orderto ascertain when the hob has been completely ground. The form of gaugeherein shown comprises a gauge member 130 (Figs. 1 and 5) mounted forsliding movement toward and away from the hob in a carrier 131, saidcarrier being slidable longitudinally of the hob on a guidebar 132. Thebar 132 is removably and stationarily supported upon two posts 1.33 onthe slide 1'. The gauging is, of course, done when the machine is idle.

In grinding a multiple thread bob the spindle 9 is indexed or turnedwith relation to the gear wheel 26 after each thread has been.

Suitable modifications are made in the change-gear train 54, 55, 56 inaccordance with changes in the number of threads of the hob.

As shown, the machine is arranged to grind a right-hand hob. To operateupon a lefthand hob an additional change gear (not shown) would beprovided in the gear train 54, 55, 56 so as to reverse the direction offeed movement of the slide 1 Changes in the gear train 74, 75 and 76 aremade as required by the number of flutes or gashes in the hob to beground, and when changing from a hob having straight flutes to onehaving spiral flutes or Vice versa. Variations in the amount of reliefof the teeth of the hobs operated upon are taken care of by changes inthe shape of the cam 71.

To dress the shaped periphery of the grind-- the base 135 toward andaway from the grinding wheel by means of a screw-threaded rod 138secured to said bracket and having a nut 139 thereon. Said'nut restsin'a recess in the base 135 and is held by the walls of said recessagainst'longitudinal movement. An arm 140 is provided at its lower endwith a rod 141 whichextends slidably through a ball 142. Said ball isrotatably mounted in a socket 143 in the lower portion of the brackct134. The lower end of the rod 141 is provided with a point 144 thatrests in a socket 145 in the lower part of the bracket 134-. The upperportion of the arm 140 is provided with a knife edge 146 arranged to bemoved along the edge of a teniplet 147. The outline of the workingportion of the templet 147 corresponds to the outline to be imparted tothe sides of the teeth of the hob; The templet 147 is arranged to besecured to the upper portion of the bracket 134 by means of screws 148and washers 149 overlying said templet. As indicated by full and dottedlines in Fig. 18, the templet maybe secured to the bracket in either oftwo positions so that the wheel may be dressed whenthe frame 93 is ineither of its two horizontal positions. At the upper end of the arm 140.is a handle portion 150. A dressing tool 151 having a point ofsufficiently hard material is located on the arm 140 in the horizontalplane of the axis of the wheel Band is secured to the arm 140 by meansof nuts 152. For convenience in locating the point of the dressing toolin the line containing the center of the ball 142 and the knife edge146; I'provide flattened pins 153 and 154 above and below the dressingtool, against which pins a straight edge may be placed to serve as aguide in positioning the dressing tool. The radius of the socket 145 issuch that as the arm 140 is oscillated upon the center of the. ball 142and moved along the edge of the template 147, the arm will be moved upand down sufficiently so that the point of' the dressing tool shalltrace, in a horizontal plane,

the hobs. I

The hob illustrated in Fig. 1 has straight flutes or gashes, that is tosay the gashes are parallel to the axis of the hob. Some hobs areprovided with spiral gashes which are normal to the ed, when dressing:1. wheel that is to be used for grinding the teeth of a spirally-gashedhob, the frame 93 is secured in horizontal position. \Vhen dressing awheel to be used for grinding the teeth of a straight gashed hob. asherein, shown. the frame 93 is secured in a position inclined to thesame degree as when grinding. I

While the wheel is being dressed. it may be rotated in a reversedirection, if desired, the belt 129 being arranged accordingly.

A decrease in the diameter of the wheel B, due to wear and dressing, isadjusted for by advancing the slide 82 with relation to the slide 69 byturning the screw 85, and by retracting the head 111 by ad usting thenuts 117.

As hereinbefore stated, the grinding wheel should be so positioned withrelation tothe hob that there shall be clearance between the wheel andthe approaching hob tooth. This result has been attained by mounting thegrinding wheel spindle in a .manner which, for the sake of clearness,may be described by saying that the spindle is at an oblique the contourof em, surface to be ground upon the teeth of thread. .As hereinbeforestatangle to the hob axis when the spindle is-in the horizontal plane ofthe hob axis. In the present instance, said angle is about 25 degrees.Because of this oblique mounting, it

will be understood that the periphery of the wheel curves away from theapproachingtooth and thus permits of grinding a relatively long surfaceon the side of each tooth, whereby I am enabled to produce a groundrelieved hob which can be resharpened a rela-.

tively large number of times without change of form or dimensions.

While I have described the present embodi for causing relative movementbetween the I wheel and the hob longitudinally of the hob,

a drive wheel concentric with the spindle for rotating the same, andadjustable means connecting-the spindle and drive wheel to permit ofrelat ve rotation between the same including an intermediate member,said intermediate member being adjustable with respect to both spindleand driving wheel and rigidly secured to each in the adjusted position.

2. hob-grinding machine having, in comb1n at1on, a support for a hob,means for rotating said support around the axis of said hob and slidingitalong the axis synchronously, a tool adapted to slide along an axisperpendicular to the axis of said hob, and

also rotatable around its axis of sliding, means for clamping said toolin adjusted :ngular position and means for sliding said 3. hob-grindingmachine having, in combinat on, a grinding wheel, a slide, means on thesl de for rotatably supporting a hob with its axls extending in thedirection of movement of the slide, a feed screw for moving the slide, anut on said screw, and manually adustable means connecting said nut tothe slide for movement of the slide with relation to the nutlongitudinally of the screw.

4. A hob-grinding machine having, in com bination, a slide. means on theslide for rotatably supporting a hob with its axis extending in thedirection of movement of the slide, a" feed screw for moving the slide,a nut on the feed screw, a nut secured upon the first mentioned nut,means rotatably connecting the second nut to the slide, and means forrotating the second nut.

5. A hob-grinding machine having, in combination, a grinding wheel, a'rotatably mounted spindle for supporting a hob, means for causingrelative movement between the wheel and the hob longitudinally 'of thehob,

' said ring and a wheel for rotating the spindle, and adjustable meansconnecting the spindle and second mentionedwheel to permit of relativerotation between the spindle and said second mentioned wheel.

6. A hob-grinding machine having, in comblnation, a hob-supportingspindle, a. ring secured to said spindle to rotate therewith, a drivewheel concentric with the spindle and rmg, and means for adjustablyconnecting wheel for relative rotaftion.

7. A hob-grinding machinehaving, in combination, means for rotatablysupporting a hob, a slide, a grinding wheel carried by the slide, andthree mutuallyindependent means for producing movement of the slidetoward and away from the hob.

8. hob-grinding machine having, in combination, a grinding wheel, aslide, means on the slide for rotatably supporting a hob with its axisextending in \the direction of movement of the slide, means for rotatingthe hob, a feed screw, a nut on the feed screw, said feed screw and nutbeing arranged to move the slide when the feed screw is-rotated, powermeans for rotating the feed screw, a clutch connecting the feed screw tosaid driving means, and manual means for rot-atmg the feed screw.

1 and a third means for moving 9. hob-grinding machine having, in,combination, means for rotatably supporting a hob,a slide mounted formovement toward and awayfrom the hob, a grinding wheel carried by theslide, relieving means adapted to reciprocate the slide toward and awayfrom the hob, adjustment means independent of said relieving means formoving the slide, the slide to withdraw the grinding wheel clear of thehob without interfering with the operation or adjustment of saidrelieving or adjustment means.

I ciprocate the same.

10. A hob-grinding machine having, in combination, two parallelspindles, change gears determining the rel'ative speed of said twospindles, one of said spindles being adapted to slide axially as well asrotate,

means for axially moving said spindle at a constant pitch, a tooladapted to reciprocate in a line perpendicular to the axis of saidslidable spindle, and a cam on the other spins dle operatively connectedto said tool to re- 11. A hob-grinding machine having, in combination,ahob-carrying spindle adapted to rotate and move axially at a constantpitch, a countershaft parallel to said spindle, means for drivingsaidcountershaft. a cam mounted for rotation on the same .axis as saidcountershaft, a connection between said cam and said countershaftadapted to transmit rotation in one direction only, a. tool slidable ona line at an angle to the axis of said spindle and an operativeconnection between said cam and said tool.

12. A grinding machine having, in combinat-ion, a work carriage, a powertransmission for rotating the work onsaidcarriagey manual adjustmentmeans interpolated insaid power transmission for synchronizing the samewith other parts of the machine, a power transmission for sliding saidcarriage, and manual adjustment means interpolated in said lastmentioned power transmission. F I W 13. A grinding machine having, incombination, a. work carriage, a power transmission to said carriageincluding a nut and a cooperating feed screw, and manual adjustmentmeans interpolated in said transmission for .manually producingindependent longitudinal adjustment ofi said carriage.

14. A grinding machine having, in combination, a carriage, a connectiontransmitting power through a plurality of intermediate elementsincluding a feed screw and oooperating nut for sliding said carriage,and

means operating on' one of said intermediate elements for manuallyproducing independent longitudinal adjustment of said carriage.

15. A grinding machine having, in combination, a carriage,a feed screwand cooperating nut, a power transmission for rotating one of said twolast mentioned elements, and a mechanical connection between the otherelement and said carriage normally constraining them to reciprocate inunison but adjustable to produce limited longitudinal displacement ofsaid carriage independent of and superposed upon the movement producedby said power transmission.

16. A relievin hob grinder having a' rotatable work spindle adapted tocarry the hob, a post, a-frame journaled in said post about an axiswhich, if extended or produced, will approximately pass through the axisof the work spindle, a grinder spindle journaled in said frame andadapted to hold the grinder in contact with the hob at a point approxi-'mat'ely in line with the axis of rotation of the frame, means for Yproducing relative travel between the post and the work spindle ina.

ment between said frame and the work spindle in a directionapproximately perpendicular to the axis of the work spindle.

17 A machine for grinding either straightgashed or spiral-gashedhobshaving a spiral series of teeth, said machine comprising, incombination, means o support the hob; a grinding wheel having aperiphery shaped to grind one side at a time of the spiral series ofteeth, aframe to support'said grinding wheel, said frame being pivotedto swing through degrees to position theperiphcry of the wheel forgrinding either side of said spiral series of teeth,-theaxis of saidframe being perpendicular to the axis of the hob, the point ofintersection of the pitch line of the hob and the line of contact of thehob and the grinding wheel being in the axis of said frame; and means to'eifect relative reciprocation of thewheel and the hob to relieve saidteethQ 18. A relieving hob grinder having means to support and rotate ahob, a' support, a

' frame journaled in said support for rotation through 180 de ees aboutan-axis which if extended or pro uced will pass approximately throughthe axis of the hob, a spindle journaled in said frame at an obliqueangle to the hob axis, a grinding wheeladapted to grind one side only ofthe hob teeth at a time andarranged to be held by said spindle incontact with the hob at a point approximately in line with the axis ofsaid frame, means for producing relative travel between the support thework spindle to eifec t the grinding of relief on the teeth of the hob.

' 19. A relieving hob grinder having means to support and rotate a hob,a support, a

frame journaled in said support for rotation through 180 degrees aboutan axis which if extended or produced will pass approximately throughthe axis of the hob, a spindle 2 journaled in said frame at an obliqueangle to the hob axis, a grinding wheel arranged to be held by saidspindle with only one tween said support and the hob in a directionapproximately perpendicular to the axis of the workv spindle to effectthe grinding of relief on the teeth of the hob.

21. A relieving hob grinder having means to support and rotate a hob, agrinding wheel adapted to 'nd one side only of the hob teeth at a time,a spindle for the wheel, means to support the spindle at either side ofa vertical plane that is perpendicular to the hob axis with the spindleperpendicular to the hob helix and oblique to the hob axis, means forproducing relative travel between the support and the hob'in a directionparallel to the axis of the hob, and means operating in timed relationwith the rotation of the hob for periodically effecting relativemovement between said support and the hob in a direction approximatelyperpendicular to the axis of the work spindle to effect the grinding ofrelief on the teeth of the hob.

In testimony whereof, I have hereunto affixed m si ature.

y 'gn JOHN EDGAR.

grinding surface in contact with the hob, means on said support at eachside of the first mentioned axis for securing said frame in positionwith said spindleperpendicular to the hob helix at either side ofsaidfirst mentioned axis, means for producing relative travel betweenthe support and the hob in a direction parallel to the axis of the hob,and means operating in timed relation with the, rotation of the hob forperiodically effecting relative movement between said support and thehob in a direction approximately perpendicular to the axis of the workspindle to iffict the grinding of relief on the teeth of the 20. Arelieving hob grinder having means to support and rotate a hob, asupport, a frame journaled in said supportfor rotation through 180degrees, a spindle journaled in said frame at an oblique angle to thehob axis, a grinding wheel arranged to be held by said spindle with onlyone grinding surface in contact with the hob mean's for producingrelative travel between the support and the hob in a direction parallelto the axis of'the hob, and means operating in timed relation with therotation .of the hob for periodically efiecting relative movementbegrinding

